Pentamidine [1,5- bis(4-amidinophenoxy)pentane] is the exemplar of a growing class of dicationic, aromatic agents active against a variety of infectious agents of significance to immunocompromised and normal individuals. Pentamidine is still an important "second line" agent in the prevention and treatment of Pneumocystis carinii infection predominant in AIDS patients. New dicationic molecules have shown reduced toxicity and broadened specificity against important fungal and protozoal pathogens. For example, DAP-092 (2,7 diamidinocarbazole dihydrochloride) is a highly promising agent against Cryptosporidium parvum (which causes diarrheal disease in normal and immunocompromised individuals) soon to go into clinical trials. Pentamidine, (although in use for over 50 years), is hampered by its toxicity and narrow therapeutic range. Measurement of pentamidine in biological samples is difficult relying on HPLC (sometimes supplemented by mass spectroscopy) and other physical methods. Recently, we have developed a facile immunoassay for pentamidine which shows promise in monitoring patient drug levels and also as a model for immunoassays for new cationic drugs. Hence, the overall goal of this proposal is to develop a practical clinical assay for a dicationic drug (pentamidine) and extend this model to a new agents (such as DAP-092) for use in preclinical and clinical trials. PROPOSED COMMERCIAL APPLICATION: Proposed commercial application not available.